<?php
    // +----------------------------------------------------------------------
    // | ThinkPHP [ WE CAN DO IT JUST THINK ]
    // +----------------------------------------------------------------------
    // | Copyright (c) 2006~2017 http://thinkphp.cn All rights reserved.
    // +----------------------------------------------------------------------
    // | Licensed ( http://www.apache.org/licenses/LICENSE-2.0 )
    // +----------------------------------------------------------------------
    // | Author: liu21st <liu21st@gmail.com>
    // +----------------------------------------------------------------------
    namespace think\model\relation;

    use think\db\Query;
    use think\Exception;
    use think\Loader;
    use think\Model;
    use think\model\Relation;

    class HasManyThrough extends Relation {
        // 中间关联表外键
        protected $throughKey;
        // 中间表模型
        protected $through;

        /**
         * 构造函数
         * @access   public
         * @param Model  $parent     上级模型对象
         * @param string $model      模型名
         * @param string $through    中间模型名
         * @param string $foreignKey 关联外键
         * @param string $throughKey 关联外键
         * @param string $localKey   关联主键
         */
        public function __construct(Model $parent, $model, $through, $foreignKey, $throughKey, $localKey) {
            $this->parent     = $parent;
            $this->model      = $model;
            $this->through    = $through;
            $this->foreignKey = $foreignKey;
            $this->throughKey = $throughKey;
            $this->localKey   = $localKey;
            $this->query      = (new $model)->db();
        }

        /**
         * 延迟获取关联数据
         * @param string   $subRelation 子关联名
         * @param \Closure $closure     闭包查询条件
         * @return false|\PDOStatement|string|\think\Collection
         */
        public function getRelation($subRelation = '', $closure = null) {
            if ($closure) {
                call_user_func_array($closure, [& $this->query]);
            }
            return $this->relation($subRelation)->select();
        }

        /**
         * 根据关联条件查询当前模型
         * @access public
         * @param string  $operator 比较操作符
         * @param integer $count    个数
         * @param string  $id       关联表的统计字段
         * @param string  $joinType JOIN类型
         * @return Query
         */
        public function has($operator = '>=', $count = 1, $id = '*', $joinType = 'INNER') {
            return $this->parent;
        }

        /**
         * 根据关联条件查询当前模型
         * @access public
         * @param mixed $where 查询条件（数组或者闭包）
         * @return Query
         */
        public function hasWhere($where = []) {
            throw new Exception('relation not support: hasWhere');
        }

        /**
         * 预载入关联查询
         * @access public
         * @param array    $resultSet   数据集
         * @param string   $relation    当前关联名
         * @param string   $subRelation 子关联名
         * @param \Closure $closure     闭包
         * @param string   $class       数据集对象名 为空表示数组
         * @return void
         */
        public function eagerlyResultSet(&$resultSet, $relation, $subRelation, $closure, $class) { }

        /**
         * 预载入关联查询 返回模型对象
         * @access public
         * @param Model    $result      数据对象
         * @param string   $relation    当前关联名
         * @param string   $subRelation 子关联名
         * @param \Closure $closure     闭包
         * @param string   $class       数据集对象名 为空表示数组
         * @return void
         */
        public function eagerlyResult(&$result, $relation, $subRelation, $closure, $class) { }

        /**
         * 关联统计
         * @access public
         * @param Model    $result  数据对象
         * @param \Closure $closure 闭包
         * @return integer
         */
        public function relationCount($result, $closure) { }

        /**
         * 执行基础查询（进执行一次）
         * @access protected
         * @return void
         */
        protected function baseQuery() {
            if (empty($this->baseQuery) && $this->parent->getData()) {
                $through      = $this->through;
                $alias        = Loader::parseName(basename(str_replace('\\', '/', $this->model)));
                $throughTable = $through::getTable();
                $pk           = (new $through)->getPk();
                $throughKey   = $this->throughKey;
                $modelTable   = $this->parent->getTable();
                $this->query->field($alias . '.*')
                            ->alias($alias)
                            ->join($throughTable, $throughTable . '.' . $pk . '=' . $alias . '.' . $throughKey)
                            ->join($modelTable, $modelTable . '.' . $this->localKey . '=' . $throughTable . '.' . $this->foreignKey)
                            ->where($throughTable . '.' . $this->foreignKey, $this->parent->{$this->localKey});
                $this->baseQuery = true;
            }
        }
    }
